3-cyano-2,4,5-trifluoro-benzoyl fluoride and intermediate products for the production thereof

ABSTRACT

The present invention relates to 3-cyano-2,4,5-trifluorobenzoyl fluoride and to intermediates for its preparation and to the process for the preparation of 3-cyano-2,4,5-trifluoro-benzoyl fluoride, which starts from 5 fluoro-1,3-xylene (VIII); which is bichlorinated in the ring in the presence of a catalyst under ionic conditions to give 2,4-dichloro-5-fluoro-1,3 dimethylbenzene (VII). The latter is chlorinated in the side chains under free-radical conditions to give 2,4-dichloro-5-fluoro-3-dichloromethyl-1 trichloromethylbenzene (VI). The latter is hydrolyzed via 2,4-dichloro-5-fluoro-3-dichloromethylbenzoic acid (V), which can be isolated if necessary, to give 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV), the aldehyde group of which is reacted to give 2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid (III), from which, with simultaneous conversion of the carboxyl group into the chlorocarbonyl group, water is eliminated using an acid chloride to give the nitrile 2,4-dichloro-3-cyano-5 fluoro-benzoyl chloride (II). Finally the nitrile is subjected to fluorine/chlorine exchange.

This application is a 371 of PCT/EP 98/02175 filed Apr. 14, 1998. Thepresent Invention relates to 3-cyano-2,4,5-trifluoro-benzoyl fluoride,to a process for its preparation, and to other novel halogenobenzenederivatives as intermediates.

3-Cyano-2,4,5-trifluoro-benzoyl chloride can be used for the preparationof antiinfective quinolonecarboxylic acids (cf. DE-A 1 963 805 No.19 606762.6=WO 97/31001). The preparation starts from2,4-dichloro-5-fluoro-3-cyanobenzoic acid and leads by a known method(cf. DE 3702393 Al) to 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride,which is then fluorinated. A disadvantage of this process is, inparticular, the Sandmeyer reaction, which proceeds with poorlyreproducible yield, using a molar amount of copper cyanide and anadditional three-fold excess of sodium cyanide to give2,4-dichloro-3-cyano-5-fluoro-benzoic acid. The use of such largeamounts of cyanide also harbours a considerable hazard potential whenthe reaction is carried out industrially.

The present invention relates to novel 3-cyano-2,4,5-trifluoro-benzoylfluoride of the formula (I)

The invention also relates to a process for the preparation of3-cyano-2,4,5-trifluoro-benzoyl chloride by chlorination of3-cyano-2,4,5-trifluoro-benzoyl fluoride.

In addition, the invention also relates to the use of3-cyano-2,4,5-trifluoro-benzoyl fluoride for the synthesis ofquinolones.

The invention further relates to a multistage process for thepreparation of 3-cyano-2,4,5-trifluoro-benzoyl fluoride, which startsfrom 5-fluoro-1,3-xylene (VIII), characterized in that5-fluoro-1,3-xylene (VIII) is bichlorinated in the ring in the presenceof a catalyst under ionic conditions to give 2,4-dichloro-5-fluoro-1,3dimethylbenzene (VII), which is then chlorinated in the side chainsunder free-radical conditions to give2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI),which is hydrolysed via 2,4-dichloro-5-fluoro-3-dichloromethylbenzoicacid (V), which can be isolated if necessary, to give2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV), the aldehyde group ofwhich is reacted to give 2,4-dichloro-5fluoro-3-N-hydroxyiminomethyl-benzoic acid (III), from which, withsimultaneous conversion of the carboxyl group into the chlorocarbonylgroup, water is eliminated using an acid chloride to give the nitrite2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride (II), which, finally, issubjected to fluorine/chlorine exchange.

Alternatively, 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV) can alsobe reacted to give 2,4-dichloro-5-fluoro-3-cyano-benzoic acid (IX),which can then be converted into the acid chloride (II).

The intermediates of the formulae (III) to (VII) are novel withoutexception and are likewise provided by the invention.

3-Cyano-2,4,5-trifluoro-benzoyl fluoride is an intermediate, readilyobtainable by the process described here, for the preparation of3-cyano-2,4,5-trifluoro-benzoyl chloride.

The process according to the invention is described in more detailbelow.

The ring chlorination of commercially available 5-fluoro-1,3-xylene(VIII) to give 2,4-dichloro-5-fluoro-1,3-dimethylbenzene (VII) iscarried out using chlorine gas.

2,4-Dichloro-5-fluoro-1,3-dimethylbenzene (VII) is novel.

The catalyst used is one or more Friedel-Crafts catalysts, preferably aLewis acid, such as, for example, iron (III) chloride or aluminiumchloride. For example, from 0.1 to 10 mol %, preferably from 0.2 to 2mol %, based on 5-fluoro-1,3-xylene, are used.

The reaction can be carried out at temperatures below room temperatureor at slightly elevated temperature. Preference is given to temperaturesbetween 0 and 40° C.

The chlorination can be carried out without a diluent or in a suitableinert diluent. Particularly suitable diluents are halogenatedhydrocarbons such as dichloro-, trichloro-, tetrachloromethane,1,2-dichloroethane or 1,2,4-trichlorobenzene. The chlorination can becarried out continuously or batchwise. In a continuous process, it iswise to proceed only to a low conversion because the chlorination doesnot take place with complete selectivity. In the batchwise procedure,chlorine is introduced in an amount up to approximately 0.8-1.1 times,preferably 0.8-0.95 times, the theoretical amount, the reaction mixtureachieving a solid consistency in the chlorination without diluent. It isalso advantageous in this connection to proceed only up to thisnot-too-high conversion because then the losses as a result ofsuperchlorination on the one hand and the space-time yield on the otherare in an optimum range.

The mixture is worked up, for example, by fractional distillation. It isadvantageous to return recovered starting material and monochlorinatedcompounds to the process.

The side-chain chlorination of 2,4-dichloro-5-fluoro-1,3-dimethylbenzene(VII) to give2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI) ispreferably carried out without a diluent using chlorine gas.

2,4-Dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI) isnovel.

The conditions for the free-radical reaction are achieved by elevatedtemperature and optional irradiation with a light source or addition ofa customary free-radical initiator. Suitable light sources areincandescent lamps such as, preferably, halogen lamps or medium- orhigh-pressure mercury vapour lamps. Suitable free-radical initiatorsare, for example, benzoyl peroxide, di-tert-butyl peroxide or2,2-azobis(isobutteronitrile) (AIBN). The reaction temperature can bebetween 80 and 200° C., preferably 100 and 180° C., particularlypreferably between 120 and 170° C.

The chlorination can be carried out continuously or batchwise. In acontinuous process, it is wise to proceed only up to a low conversionbecause the chlorination does not take place with complete selectivity.In the batchwise procedure, chlorine is introduced in an amount up toapproximately 0.8-1.2 times, preferably 0.95-1.15 times the theoreticalamount, corresponding to from 40 to 75%, preferably from 65 to 75%,conversion to the desired product.

The reaction mixture can be worked up, for example, by fractionaldistillation or recrystallization from a suitable solvent such as, forexample, methanol. Preference is given to distillation. Insufficientlychlorinated compounds can be introduced again into the chlorination.

The chlorinated side chains are hydrolysed using a protic acid,optionally in the presence of water. Suitable protic acids are mineralacids such as, for example, sulphuric acid, hydrochloric acid orphosphoric acid, and organic acids such as, for example, formic acid,acetic acid or oxalic acid, and mixtures thereof and with a proticsolvent such as, for example, water.

Depending on the type, concentration and amount of acid and reactiontemperature, it is possible to carry out the hydrolysis of2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI) togive 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV) in one or twosteps. Because the trichloromethyl group is hydrolysed significantlymore quickly, 2,4-dichloro-5-fluoro-3-dichloromethylbenzoic acid (V)can, if the reaction conditions are suitable, be isolated directly andconverted to (IV) in a further hydrolysis step. As far as the overallprocess of the preparation of 3 cyano-2,4,5-trifluoro-benzoyl fluorideaccording to the invention is concerned, it is advantageous to carry outthe hydrolysis in one step.

2,4-Dichloro-5-fluoro-3-formyl-benzoic acid (IV) and2,4-dichloro-5-fluoro-3 dichloromethylbenzoic acid (V) are novel.

The amount of protic acid is unimportant. The acid, for example, isinitially introduced and the molten aromatic compound (VI) or (V) isadded. Preference is given to using sufficient acid (mixture) for thereaction mixture to remain stirrable.

The temperature for the hydrolysis can be varied within a wide rangedepending on the desired product, acid and reaction time. Thetemperature is generally from 0 to 100° C.

The product can be isolated, for example, by precipitation with waterand removal by filtration or extraction.

The oxime (III) is prepared from 2,4-dichloro-5-fluoro-3-formyl-benzoicacid (IV) by a generally known method.

2,4-Dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid (III) isnovel.

The reagent used is a salt of hydroxylamine such as, for example, thehydrochloride or sulphate, or also the free base.

If a salt of hydroxylamine is used, the reaction is carried out in thepresence of an acid acceptor. Suitable acid acceptors are customaryinorganic or organic bases. These include, preferably, the hydroxides,alkoxides, acetates, carbonates and hydrogen carbonates of alkalineearth metals or alkali metals, such as, for example, the hydroxides ofsodium, potassium or ammonium, sodium methoxide, sodium ethoxide,potassium tert-butoxide, the acetates of sodium, potassium, calcium orammonium, the carbonate of sodium, potassium or ammonium, the hydrogencarbonates of sodium or potassium, and tertiary amines, such astrimethylamine, triethylamine, tributylamine, N,N-dimethylaniline,N,N-dimethyl-benzylamine, pyridine, N-methylpiperidine,N-methylmorpholine, N,N-dimethylaminopyridine, diazabicyclooctane(DABCO), diazabicyclononene (DBN) or diazabicycloundecene (DBU).

The reaction is carried out in the presence of a diluent. Suitablediluents are water, organic solvents and any mixtures thereof. Exampleswhich may be mentioned are: ethers, such as diethyl ether, diisopropylether, methyl t-butyl ether, methyl t-amyl ether, dioxane,tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyleneglycol dimethyl ether or anisole; nitriles, such as acetonitrile,propionitrile, n- or i-butyronitrile; alcohols, such as methanol,ethanol, n- or i-propanol, n-, iso-, sec- or tert-butanol, ethanediol,propane-1,2-diol, ethoxyethanol, methoxyethanol, diethylene glycolmonomethyl ether, diethylene glycol monoethyl ether; water.

The temperature for the reaction can be varied within a relatively widerange. It is generally chosen to be between 10 and 100° C., preferablybetween 20 and 80° C.

Per mol of formylbenzoic acid (IV), from 1 to 1.5 equivalents ofhydroxylamine (salt) are used, and from 200 to 2000 ml, preferably from500 to 1000 ml, of diluent are used. Per equivalent of hydroxylamine,from 1 to 5, preferably from 1.1 to 3, equivalents of acid acceptor areused.

For work-up, the reaction mixture is acidified, for example using amineral acid, and, where appropriate, the product is extracted using asuitable solvent such as, for example, methyl tert-butyl ether, or thesolid is filtered off.

If the reaction of (IV) with hydroxylamine or a salt of hydroxylamine iscarried out in the presence of formic acid, then the reaction productobtained is the nitrile (IX). Preference is given to using hydroxylaminehydrochloride.

The reaction can be carried out in the presence of a diluent. Suitablediluents are water, organic solvents and any mixtures thereof.Preferably, the reaction is carried out in from 85% to 98% strengthaqueous formic acid.

The temperature of the reaction can be varied in a relatively widerange. It is generally chosen to be between 10 and 120° C., preferablybetween 50 and 110° C.

Per mol of (IV), from 1 to 1.5 equivalents of hydroxylamine (salt) areused, and from 100 to 3000 ml, preferably from 500 to 1500 ml, ofaqueous formic acid are used.

The starting materials can be added in different orders. For example,all of the starting materials can be initially introduced and thenheated up to the reaction temperature together. It is, however, alsopossible to initially introduce the hydroxylamine (salt) into theaqueous formic acid, and introduce the starting material (IV) at thereaction temperature.

Alternatively, the starting material (IV), which can also be usedmoistened with sulphuric acid, can be introduced into the aqueous formicacid, and the hydroxylamine (salt) or a solution of the hydroxylamine(salt) in water or aqueous formic acid can be metered in at the reactiontemperature.

For work-up, the mixture is further diluted with water, and (IX) isfiltered off as solid.

3-Cyano-2,4-dichloro-5-fluorobenzoic acid (IX) is converted into benzoylchloride (II) using a chlorinating agent as reagent.

Suitable chlorinating agents are those agents given below under thereaction conditions stated there.

The preparation of 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride (II)by elimination of water from2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid (III) withsimultaneous conversion of the carboxylic acid function into thecarbonyl chloride takes place using a chlorinating agent as reagent.

Suitable chlorinating agents are inorganic or organic acid chlorides,such as, for example, phosgene (carbonyl dichloride) or the syntheticequivalents trichloromethyl chloroformate or bis(trichloromethyl)carbonate, oxalyl chloride, acetyl chloride, thionyl chloride, sulphurylchloride, phosphorous trichloride, phosphorous pentachloride orphosphorous oxychloride and mixtures thereof. Preference is given tophosgene or thionyl chloride.

The reaction can be carried out in the presence or absence of a suitablediluent. Suitable diluents for this purpose are organic solvents, anacid chloride which is liquid under the reaction conditions, i.e. thereagent itself, and any mixtures thereof. Examples of organic solventswhich may be mentioned are: aliphatic, alicyclic or aromatichydrocarbons, such as, for example, petroleum ether, hexane, heptane,cyclohexane, methylcyclohexane, benzene, toluene, xylene or decalin;halogenated hydrocarbons, such as, for example, chlorobenzene,dichlorobenzene, methylene chloride, chloroform, tetrachloromethane,dichloroethane, trichloroethane or tetrachloroethylene; ethers, such asdiethyl ether, diisopropyl ether, methyl t-butyl ether, methyl t-amylether, dioxane, tetrahydrofuran, 1,2-dimethoxyethane,1,2-diethoxyethane, diethylene glycol dimethyl ether or anisole.

The oxime compound and chlorinating agent can be added in any order. Ina preferred embodiment, the solvent-free reagent is initiallyintroduced, and 2,4 dichloro-5-fluoro-3-N-hydroxyiminomethyl acid ismetered in continuously or in portions at a rate of controllable gasevolution (hydrogen chloride and in some cases other gases such ascarbon dioxide or sulphur dioxide).

From 2 to 10 mol of acid chloride are generally used per mol of compound(III). It is also possible to use a larger excess, particularly when theacid chloride also serves as diluent.

The temperature in the reaction can be varied in a relatively widerange. It is generally chosen to be between 0 and 150° C., preferablybetween 30° C. and boiling temperature. The process is generally carriedout under atmospheric pressure. It is also possible to carry out thereaction under reduced or elevated pressure. For example, when phosgeneis used, it is wise to keep it liquid at a temperature above the boilingpoint at atmospheric pressure and to release the gases which areliberated by means of a pressure-relief device.

The mixture can be worked up, for example, by fractional distillation.

The final fluorine/chlorine exchange takes place nucleophilically usinga fluoride source.

Suitable fluoride sources are, for example, metal fluorides, preferablyalkali metal fluorides, such as, for example, potassium fluoride orcaesium fluoride.

The fluorination is carried out in the presence of a diluent. Suitablediluents are polar aprotic solvents such as, for example, amides, suchas N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformanilide,N-methylpyrrolidone or hexamethylphosphoramide; ureas, such asN,N-dimethylpropyleneurea, N,N-dimethylethyleneurea; sulphoxides, suchas dimethyl sulphoxide; sulphones, such as sulpholane.

The fluorination can also be carried out in the presence of knowncatalysts for halex reactions.

Per mol of 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride, from 3 to 10mol, preferably from 3.4 to 8 mol, particularly preferably from 3.7 to 6mol of fluoride are used.

The fluorination is carried out at elevated temperature. The temperatureis generally from 100 to 250° C., preferably from 130 to 200° C.

Work-up can, for example, involve distillation of the product underreduced pressure, or extraction using a solvent and subsequentfractional distillation.

The preparation of 3-cyano-2,4,5-trifluoro-benzoyl chloride from3-cyano-2,4,5-trifluoro-benzoyl fluoride (I) according to the inventionis carried out analogously to known processes for the rechlorination ofcarbonyl fluorides. Reagents which are suitable for this purpose aresilicon chlorides, such as, for example, silicon tetrachloride,trimethylchlorosilane or dimethyldichlorosilane; or calcium chloride, ineach case in the presence of catalytic amounts of a Lewis acid, such as,for example, aluminium chloride or boron trichloride; or said or otherchlorine-containing Lewis acids themselves.

Per mol of compound (I), from 1 to 2 equivalents of reagent and, whereappropriate, from 0.01 to 0.1 mol of Lewis acid are generally used.

The temperature in the reaction can be varied within a relatively widerange. The reaction is generally carried out at from 20 to 150° C. whensilicon chlorides and Lewis acids are used, and at from 120 to 200° C.when calcium chloride is used.

Work-up is preferably by vacuum distillation.

It is extremely surprising that the ring chlorination of5-fluoro-1,3-xylene to give 2,4-dichloro-5-fluoro-1,3-proceeds with veryhigh selectivity, without which the synthesis sequence according to theinvention would not be possible.

Further details of the processes are given in the examples below,without the invention being limited thereby.

EXAMPLE 1 Preparation of 2,4-dichloro-5-fluoro-1,3-dimethylbenzene

a) solvent-free

1 g of anhydrous iron(III) chloride were introduced into 124 g of 3,5-dimethyl-fluorobenzene, and chlorine was introduced at the rate of thereaction (about 4 h). The reaction is initially slightly exothermic(temperature increase from 24 to 32° C.) and was maintained below 30° C.by gentle cooling. After 120 g of chlorine had been introduced, themixture solidified. According to GC analysis, 33.4% of monochlorinatedcompound, 58.4% of desired product and 5% of superchlorinated compoundshad formed. After the hydrogen chloride had been stripped off,distillation was carried out in a water-jet vacuum on a column.

In the initial fraction, at 72-74° C./22 mbar, 49 g of2-chloro-5-fluoro-1,3-dimethylbenzene were obtained. After anintermediate fraction of 5 g, at 105° C./22 mbar, 75 g of2,4-dichloro-5-fluoro-1,3-dimethylbenzene passed over.

Melting range: 64-65° C.

b) in 1,2-dichloroethane

1 kg of 3,5-dimethyl-fluorobenzene and 15 g of anhydrous iron(III)chloride were introduced into 1 l of 1,2-dichloroethane, and chlorinewas introduced at the rate of the reaction (about 4 h). The reaction isinitially slightly exothermic (temperature increase from 24 to 32° C.)and was maintained below 30° C. by gentle cooling. After 1200 g ofchlorine had been absorbed, according to GC analysis, 4% ofmonochlorinated compound, 81.1% of desired product and 13.3% ofsuperchlorinated compounds had formed. After the solvent and hydrogenchloride had been distilled off, distillation was carried out in awaterjet vacuum on a column.

In the initial fraction, 40 g of 2-chloro-5-fluoro-1,3-dimethylbenzenewere obtained. After a small intermediate fraction, 1115 g of2,4-dichloro-5-fluoro-1,3-dimethylbenzene passed over at 127-128° C./50mbar.

EXAMPLE 2 2,4-Dichloro-5-nuoro-3-dichloromethyl-1-trichloromethylbenzene

1890 g of 2,4-dichloro-5-fluoro-1,3-dimethylbenzene were introduced intoa photochlorination apparatus with chlorine inlet and outlet for thehydrogen chloride to a scrubber and a light source in the vicinity ofthe chlorine inlet pipe, and chlorine was metered in at from 140 to 150°C. After 30 h, 3850 g of chlorine had been introduced. The content ofdesired product was 71.1% according to GC analysis; the proportion ofinsufficiently chlorinated compounds was 27.7%.

Distillation over a 60 cm column containing Wilson spiral gave aninitial fraction of 1142 g, which could be reintroduced into thechlorination. The main fraction at 160-168° C./0,2 mbar gave 2200 g of2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene having amelting range of 74-76° C.

After recrystallization of a sample from methanol, the melting point was81-82° C. The initial fraction from this reaction can be reintroducedinto the chlorination with new starting material (1555 g). This gave1377 g of initial fraction and 2465 g of main fraction with a purity of97.4%.

EXAMPLE 3 2,4-Dichloro-5-fluoro-3-formyl-benzoic acid

At 70° C., 2500 ml of 95% strength sulphuric acid were initiallyintroduced into a stirred apparatus fitted with a gas outlet, and 500 gof molten 2,4-dichloro-5-fluoro3-dichloromethyl-1-trichloromethlbenzenewere added dropwise with stirring. After a short while, evolution ofhydrogen chloride commenced. After 2 h everything had been metered inand stirring was continued until the evolution of gas ceased. After thereaction mixture had cooled to 20° C., it was discharged onto 4 kg ofice, and the precipitated solid was filtered off with suction. Theproduct was then washed with water and dried. The yield of2,4-dichloro-5-fluoro-3-formyl-benzoic acid was 310 g.

Melting range: 172-174° C.

Repetition of the experiment using 2390 g of starting material, 7170 mlof sulphuric acid gave 1540 g of product (97.8% purity).

EXAMPLE 4 2,4-Dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid

80 g of hydroxylammonium chloride in 500 ml of ethanol were introducedinto a stirred apparatus, and 200 ml of 45% strength sodium hydroxidesolution were added dropwise, and 200 g of2,4-dichloro-5-fluoro-3-formyl-benzoic acid were then introduced at40-45° C. The reaction was slightly exothermic and stirring wascontinued for 5 h at 60° C. After the mixture had been cooled to roomtemperature, the pH was adjusted to <3 by the dropwise addition ofhydrochloric acid. The product was taken up in tert-butyl methyl ether,and the organic phase was separated off. The solvent was distilled offto leave 185 g of 2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoicacid.

Melting range: 190-194° C.

Repetition of this example in water instead of ethanol using 60.5 g ofhydroxylammonium chloride in 363 ml of water, 150 ml of 45% NaOH, 150 gof starting material gave 150 g of product (93.4% purity).

EXAMPLE 5 2,4-Dichloro-3-cyano-5-nuoro-benzoylchloride

600 ml of thionyl chloride were introduced into a stirred apparatusfitted with a metering device and a gas outlet leading to a scrubber viaa reflux condenser, and, at 20° C., 210 g of starting material wereintroduced at the rate of hydrogen chloride/sulphur dioxide evolution.At the end of the addition, the mixture was heated to reflux until theevolution of gas ceased. The mixture was then distilled. In the boilingrange from 142-145° C./10 mbar, 149 g of2,4-dichloro-3-cyano-5-fluorobenzoylchloride were obtained (contentaccording to GC: 98,1%).

Melting range: 73-75° C.

Repetition of this example using 450 g of phosphorous oxychloride in 200ml of chlorobenzene as chlorinating agent gave, from 80 g of startingmaterial (80%), 48 g of product (89.0% purity).

EXAMPLE 6 3-Cyano-2,4,5-trifluoro-benzoyl fluoride

50 g of potassium fluoride were suspended in 120 ml of tetramethylenesulphone, and the suspension is dried by gently distilling it at 15 mbar(about 20 ml). 50.4 g of 2,4 dichloro-3-cyano-5-fluoro-benzoyl chloridewere then added, and the mixture was stirred with the exclusion ofmoisture at an internal temperature of 180° C. for 12 hours. Vacuumdistillation gave 32.9 g of 3-cyano-2,4,5-trifluoro-benzoyl fluoride inthe boiling range from 98-100° C./12 mbar.

EXAMPLE 7 3-Cyano-2,4,5-trifluoro-benzoyl chloride

76.6 g of 3-cyano-2,4,5-trifluoro-benzoyl fluoride were initiallyintroduced together with 1 g of anhydrous aluminium chloride at 60-65°C., and 25 g of silicon tetrachloride were then added dropwise at therate of gas evolution. After the evolution of gas at 65° C. had ceased,the mixture was distilled under reduced pressure. In the boiling rangefrom 120-122° C./14 mbar, 73.2 g of 3-cyano-2,4,5-trifluoro-benzoylchloride passed over.

EXAMPLE 8 3-Cyano2,4-dichloro-5-fluorobenzoic acid

162 g of hydroxylamine hydrochloride were introduced into 2000 ml offormic acid (technical-grade, 85% strength). At 95° C., 950 g of2,4-dichloro-5-fluoro-3-formylbenzoic acid (moistened with sulphuricacid, 42% strength) were introduced. As a result, the mixture foamedbriefly and then a clear solution was immediately obtained. The mixturewas then stirred for 4 hours at from 100 to 105° C. (reflux).

After the mixture had been cooled to room temperature, it was pouredonto water, thoroughly stirred, filtered with suction and dried. Thisgave 364 g (90.3% of theory) of 3-cyano-2,4-dichloro-5-fluorobenzoicacid with a content, according to GC, of 97.7%.

EXAMPLE 9 3-Cyano-2,4-dichloro-5-fluorobenzoyl chloride

4100 ml of thionyl chloride and 41 ml of pyridine were introduced into astirred apparatus fitted with metering device and gas outlet leading toa scrubber via a reflux condenser, and, at 20° C., 2050 g of3-cyano-2,4-dichloro-5-fluorobenzoic acid (99.5% strength) wereintroduced at the rate of hydrogen chloride/sulphur dioxide evolution.At the end of the addition, the mixture was heated to reflux until theevolution of gas ceased. The mixture was then distilled. In the boilingrange from 142 to 145° C./10 mbar, 2150 g (95.7% of theory) of3-cyano-2,4-dichloro-5-fluorobenzoyl chloride were obtained (contentaccording to GC: 98.0%).

What is claimed is:
 1. 3-Cyano-2,4.5-trifluoro-benzoyl fluoride of theformula (I)


2. Process for the preparation of 3-cyano-2,4,5-trifluoro-benzoylfluoride of the formula (I) according to claim 1, wherein3-cyano-2,4-dichloro5-fluoro-benzoyl chloride is reactednucleophilically with a fluoridizing agent according to the followingequation: